(a) Technical Field
The present disclosure relates to a method for improving freezing resistance of a membrane electrode assembly, and more particularly, to manufacturing a membrane electrode assembly including conducting drying and heat treatment to minimize the formation of macro-cracks and micro-cracks in the electrode which reduces water permeation of the electrode.
(b) Background Art
Generally, polymer electrolyte membrane fuel cells (PEMFCs) are used as fuel cells for vehicles. In particular, for PEMFCs to normally exert a high power of at least several tens of kW, the fuel cells should stably operate within a wide current density range. The reaction of the fuel cell to generate electricity occurs in a membrane electrode assembly (MEA) including an electrolyte membrane and electrodes consisting of an anode and a cathode. Hydrogen supplied to the anode, which is an oxidation electrode of the fuel cell, is split into a proton and an electron. The proton moves via the electrolyte membrane to the cathode (e.g., a reduction electrode) and the electron moves via an exterior circuit to the cathode.
An oxygen molecule, the proton and the electron react with one another at the cathode. Electricity and heat are simultaneously produced and water (H2O) is produced as a by-product. When water produced by electrochemical reaction in the fuel cell is present in an appropriate amount, the water maintains humidification of the membrane electrode assembly. However, when water is excessively produced but is not adequately removed, flooding occurs at a high current density. The flood water prevents reactive gases from being effectively supplied into the fuel cell, thus causing voltage loss.
In addition, water that permeates into the electrode may freeze and the electrode may fracture at a temperature less than zero degrees Celsius. Thus, to stably operate electric vehicles using fuel cells (fuel cell electric vehicles, FCEVs) during extreme temperatures, resistance to formation and growth of fuel cells at a temperature below zero degrees Celsius should be sufficiently enhanced. Accordingly, it is important to improve freezing resistance of an electrode in the membrane electrode assembly having poor freezing resistance. Accordingly, a demand exists for development of methods that are simpler and effectively improve freezing resistance.
The above information disclosed in this section is merely for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the related art that is already known in this country to a person of ordinary skill in the art.